NCA Format

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The entire raw NCAs are encrypted.

The only known area which is not encrypted in the raw NCA is the logo section, when the NCA includes that section. Everything else documented on this page is for the plaintext version of that data.

Encryption

The first 0xC00 bytes are encrypted with AES-XTS with sector size 0x200 with a non-standard "tweak" (endianness is reversed, see here), this encrypted data is an 0x400 NCA header + an 0x200 header for each section in the section table.

Header

Offset Size Description
0x0 0x100 RSA-2048 signature over the 0x200-bytes starting at offset 0x200 using fixed key.
0x100 0x100 RSA-2048 signature over the 0x200-bytes starting at offset 0x200 using key from NPDM, or zeroes if not a program.
0x200 0x4 Magicnum "NCA3"
0x204 0x1 0 for system NCAs. 1 for a NCA from gamecard.
0x205 0x1 Content Type (0=Program, 1=Meta, 2=Control, 3=Manual, 4=Data)
0x206 0x1 Crypto Type. Only used stating with 3.0.0. Normally 0. 2 = Crypto supported starting with 3.0.0.
0x207 0x1 Key index, must be 0-2.
0x208 0x8 Size of the entire NCA.
0x210 0x8 titleID
0x21C 0x4 sdk_version. byte0 is normally 0? Compared with a required minimum-value(0x000B0000). Matches this string from codebin: "FS_ACCESS: { sdk_version: {byte3}.{byte2}.{byte1}, ...".
0x220 0x1 Crypto-Type2. 0x3 = Crypto supported starting with 3.0.1. 0x4 = Crypto supported starting with 4.0.0.
0x230 0x10 Rights ID (Ticket)
0x240 0x10*0x4(0x40) Table for each section, see below.
0x280 0x20*0x4(0x80) Table of SHA256 hashes, over each 0x200-byte Section Header Block.
0x300 0x10*0x4(0x40) Key area


The header is 0x400-bytes, at NCA+0.

When the above "Crypto Type" field is 0x2 on >=v3.0, different {crypto/keydata} is used for the sections' data. With system content, this is used with every ncatype except ncatype0. The only other exception is {data-content} for the firm titles: this is required in order for older-system-versions to install it.

Crypto-Type2 0x3(with the above crypto-type value) is used for all 3.0.1 sysmodules and the System_Version_Title.

With 3.0.2, all updated titles use the crypto from 3.0.1 for non-ncatype0, except for firm {data-content}.

Note: in some cases various game content uses the above newer crypto as well.

The keyindex passed to <key-generation-related code> is determined as follows:

  • Pre-3.0.0: The ncahdr keyindex field(0x207) is passed directly.
  • 3.0.0+: It's determined using ncahdr keyindex(0x207) and "Crypto Type"(0x206). The latter field must be 0-2. In each ncahdr_keyindex block, it executes "if(ncahdr_x206>=3)<panic>", but that won't trigger due to the earlier check. The end result is basically the same as pre-3.0.0, except when ncahdr_x206 == 0x2, final_index is new_base_index+ncahdr_keyindex. Actual implementation loads index from u32_array[ncahdr_crypto_type], where the address of u32_array is different for each ncahdr_keyindex.
  • 3.0.1+: The dedicated range check for ncahdr_x206("Crypto Type") was removed, since the updated code no longer needs it. The output from a function masked with 0xFF is now used instead of ncahdr_x206(ncahdr_crypto_type). The range check for that field was changed from {ncahdr_x206 check with panic described above}, to "if(index>=4)final_index=10;"(skips accessing the array and uses 10 directly). The arrays were updated with an additional entry: final_index=v301_base_index+ncahdr_keyindex.
    • The keydata for the above index10 is not(?) known to be initialized.
    • The new function called by the code described above does:
    • if(ncahdr_x206 < ncahdr_x220){ret = ncahdr_x220; } else { ret = ncahdr_x206; } return ret;

Section Table Entry

Offset Size Description
0x0 0x4 Media offset
0x4 0x4 Media end-offset
0x8 0x4 Unknown
0xC 0x4 Unknown

Entry size is 0x10-bytes.

Media offset is absoluteoffset/{mediasize}, where mediasize is hard-coded to 0x200.

Section Header Block

Offset Size Description
0x0 0x1  ?
0x1 0x1  ?
0x2 0x1  ?
0x3 0x1 Filesystem type. 0x2 = PFS0, 0x3 = RomFS, everything else is invalid.
0x4 0x1 Crypto type. 0 and >4 are invalid. 1 = none(plaintext from raw NCA). 2 = other crypto. 3 = regular crypto. 4 = unknown.
0x5 0x1 Padding?
0x8 FS-specific superblock.
0x100  ? Optional BKTR header. Can be used with any section, but only known to be used with game-updates RomFS.

The Section Header Block for each section is at absoluteoffset+0x400+(sectionid*0x200), where sectionid corresponds to the index used with the entry/hash tables.

The total size is 0x200-bytes.

PFS0 superblock

Offset Size Description
0x8 0x20 SHA256 hash over the hash-table at section-start+0 with the below hash-table size.
0x28 0x4 Block size in bytes.
0x2C 0x4 Must be 0x2.
0x30 0x8 Offset of hash-table. Normally zero?
0x38 0x8 Size of hash-table.
0x40 0x8 Offset relative to section-start where the PFS0 header is located.
0x48 0x8 Actual byte-size of the PFS0 filesystem relative to the PFS0 header.
0x50 0xF4 Normally zeros.
0x144  ? 0x1?
0x148 0xB8 Normally zeros.

This documents the structure of Section Header Block +0 for PFS0.

RomFS superblock

Offset Size Description
0x8 0xE0 IVFC header. Basically the same as Savegames IVFC except with 2 more levels and +0x0C is non-zero, see below.

This documents the structure of Section Header Block +0 for RomFS.

IVFC

Start Length Description
0x00 4 Magic ("IVFC")
0x04 4 Magic Number (0x20000)
0x08 4 Master hash size?
0x0C 4 Usually 7? Unknown, could be related to total number of levels maybe?
0x10 8 Level 1 offset
0x18 8 Level 1 size
0x20 4 Level 1 block size, in log2
0x24 4 Reserved
0x28 8 Level 2 offset
0x30 8 Level 2 size
0x38 4 Level 2 block size, in log2.
0x3C 4 Reserved
0x40 8 Level 3 offset
0x48 8 Level 3 size
0x50 4 Level 3 block size, in log2.
0x54 4 Reserved
0x58 8 Level 4 offset
0x60 8 Level 4 size
0x68 4 Level 4 block size, in log2.
0x6C 4 Reserved
0x70 8 Level 5 offset
0x78 8 Level 5 size
0x80 4 Level 5 block size, in log2.
0x84 4 Reserved
0x88 8 Level 6 offset
0x90 8 Level 6 size
0x98 4 Level 6 block size, in log2.
0x9C 4 Reserved
0xA0 32 Unknown, reserved?
0xC0 32 Hash

BKTR

Start Length Description
0x0 0x8 Offset
0x8 0x8 Size
0x10 0x4 "BKTR"
0x14 0x4 u32, must be <=1.
0x18 0x4 s32, must be >=1.
0x1C 0x4  ?
0x20 0x20 Same as the above 0x20-bytes except with different data.
0x40 0x4?  ?
0x44 0x4?  ?

Using this header is enabled when offset 0x8 in this header is non-zero.

The above byte-offsets are relative to the start of the section-data.

The two sections specified by the two BKTR entries are usually(?) at the very end of the section data(section_endoffset-{size of BKTR sections}).

Logo section

This is a PFS0. See here for the mounted-FS logo contents.

ExeFS section

This is a PFS0.

See here for mounted-FS ExeFS contents.

Game-updates

The section-data for the ncatype1 RomFS section(section1) is a place-holder: it's identical to section0(ExeFS). The RomFS-superblock for this section is used with other data. The RomFS data seems to stored under multiple ncatype6 content, at the "section0_pfs0/fragment" file?

PFS0

Offset Size Description
{Hash-table offset from superblock} {Hash-table size from superblock} Table of SHA256 hashes.
{Hash-table <offset+size> from superblock} Zeros for alignment to {alignment size}.
{PFS0 offset from superblock} {PFS0 size from superblock} The actual PFS0.

This is the FS which has magicnum "PFS0" at header+0. This is very similar to HFS0. A tool for extracting this FS is available here.

The hash table is hashes for every {Block size from superblock} starting at the PFS0 header. The size used for the last hash is {PFS0 filesystem size from superblock} - offset_relativeto_header.

See also the PFS0 superblock above.

Offset Size Description
0x0 0x4 "PFS0" Magic
0x4 0x4 Number of files
0x8 0x4 Size of the string table
0xC 0x4 Zero/Reserved
0x10 X File Entry Table
0x10 + X Y String Table
0x10 + X + Y Z Raw File Data

Where File Entry Table consists of Number of Files FileEntries:

Offset Size Description
0x0 0x8 Offset of file in Data
0x8 0x8 Size of file in Data
0x10 0x4 Offset of filename in String Table
0x14 0x4 Normally zero?